Pi Ceti

Pi Ceti
Location of Pi Ceti (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cetus[1]
Right ascension 02h 44m 07.348s[2]
Declination −13° 51′ 31.28″[2]
Apparent magnitude (V) 4.238[3]
Characteristics
Evolutionary stage main sequence[4]
Spectral type B7 V[5] or B7 IV[6]
U−B color index −0.396[3]
B−V color index −0.130[3]
Astrometry
Radial velocity (Rv)14.98±0.25[7] km/s
Proper motion (μ) RA: −8.394 mas/yr[2]
Dec.: −23.592 mas/yr[2]
Parallax (π)8.4022±0.1945 mas[2]
Distance388 ± 9 ly
(119 ± 3 pc)
Absolute magnitude (MV)−1.16[1]
Orbit[8]
Period (P)2,722±14 d
Eccentricity (e)0.00±0.07
Periastron epoch (T)2444852±29 JD
Argument of periastron (ω)
(secondary)		0.0°
Semi-amplitude (K1)
(primary)		4.33±0.25 km/s
Details[9]
π Cet A
Mass4.4±0.2 M☉
Radius4.3±0.3 R☉
Luminosity468 L☉
Surface gravity (log g)3.8±0.2 cgs
Temperature12,900±400 K
Metallicity [Fe/H]0.28±0.16[10] dex
Rotational velocity (v sin i)20.9±1.2 km/s
Age0.3+0.1
−0.1 Myr
Other designations
π Cet, 89 Ceti, BD−14 519, FK5 97, HD 17081, HIP 12770, HR 811, SAO 148575[11]
Database references
SIMBADdata

Pi Ceti a binary star system in the equatorial constellation of Cetus. Its name is a Bayer designation that is Latinized from π Ceti, and abbreviated Pi Cet or π Cet. The system is located near the eastern boundary of the constellation and is sometimes portrayed as forming part of the Eridanus constellation's asterism.[12] It is visible to the naked eye as a point of light with an apparent visual magnitude of 4.238.[3] Observed to have a half yearly parallax shift of 8.30 mas as seen from Earth,[2] it is located at a distance of approximately 393 light years from the Sun. The system is drifting further away from the Sun with a line of sight velocity component of +15 km/s.[7]

This is a single-lined spectroscopic binary system with a nearly circular orbit and a period of 7.45 years. The fact that the system has a negligible eccentricity is surprising for such a long period, and may suggest that the secondary is a white dwarf that had its orbit circularized during a mass-transfer event.[8]

The primary, component A, is a normal B-type star[9] that has been given stellar classifications of B7 V[5] and B7 IV.[6] It appears very young – less than half a million years in age – and may still be on a pre-main sequence track. The star shows no magnetic field but it does emit an infrared excess.[9]

Name

This star, along with ε Cet, ρ Cet and σ Cet, was Al Sufi's Al Sadr al Ḳaiṭos, the Whale's breast/chest (upper torso).[13] Per Jack Rhoads's Reduced Star Catalog Containing 537 Named Stars, Al Sufi's numerically ordered stars (1 to 4), were ρ (rho), σ (sigma), ε (epsilon) and this star.[14]

In Chinese, 天苑 (Tiān Yuàn), meaning Celestial Meadows, refers to an asterism consisting of π Ceti, and 15 stars in Eridanus: γ, π, δ, ε, ζ, η, and the string of τ (Tau)1, 2, 3, 4, 5, 6, 7, 8 and 9. Consequently, the Chinese name for the star is 天苑七 (Tiān Yuàn qī) meaning Celestial Meadows: seven.[15]

References

  1. ^ a b Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
  2. ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023), "Gaia Data Release 3. Summary of the content and survey properties", Astronomy and Astrophysics, 674: A1, arXiv:2208.00211, Bibcode:2023A&A...674A...1G, doi:10.1051/0004-6361/202243940, S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. ^ a b c d Gutierrez-Moreno, Adelina; et al. (1966), "A System of photometric standards", Publications of the Department of Astronomy University of Chile, 1, Publicaciones Universidad de Chile, Department de Astronomy: 1–17, Bibcode:1966PDAUC...1....1G.
  4. ^ Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy and Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691.
  5. ^ a b Buscombe, W. (1962), "Spectral classification of Southern fundamental stars", Mount Stromlo Observatory Mimeogram, 4: 1, Bibcode:1962MtSOM...4....1B.
  6. ^ a b Hohle, M. M.; et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355, S2CID 111387483.
  7. ^ a b Pourbaix, D.; et al. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727–732. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213. S2CID 119387088.
  8. ^ a b Lacy, C. H. S.; et al. (March 1997), "The Spectroscopic Orbit of Pi Ceti", Astronomical Journal, 113: 1088, Bibcode:1997AJ....113.1088L, doi:10.1086/118325.
  9. ^ a b c Folsom, C. P.; et al. (May 2012), "Chemical abundances of magnetic and non-magnetic Herbig Ae/Be stars", Monthly Notices of the Royal Astronomical Society, 422 (3): 2072–2101, arXiv:1202.1845, Bibcode:2012MNRAS.422.2072F, doi:10.1111/j.1365-2966.2012.20718.x, S2CID 119100447.
  10. ^ Prugniel, Ph.; et al. (July 2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics, 531: A165, arXiv:1104.4952, Bibcode:2011A&A...531A.165P, doi:10.1051/0004-6361/201116769, S2CID 54940439.
  11. ^ "pi. Cet", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2026-03-06.
  12. ^ Lovi, George (1957), Mayall, R. Newton (ed.), "Two misplaced stars", AAVSO Abstracts: papers presented at the 46th Spring meeting, May 31 – June 2, 1957, p. 4.
  13. ^ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc., p. 162, ISBN 0-486-21079-0, retrieved 2010-12-12.{{citation}}: CS1 maint: ignored ISBN errors (link)
  14. ^ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology, retrieved 2026-03-06.
  15. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 12 日 Archived 2011-05-22 at the Wayback Machine
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